LM2747-19AEVAL

User's Guide SNVA245A – May 2007 – Revised May 2013 AN-1641 LM2747-19A Demo Board 1 Introduction This user's guide describes the LM2747 printed circuit board (PCB) design and provides an example typical application circuit. The LM2747 is a voltage mode PWM buck controller that implements synchronous rectification. It provides a low cost, high power density, and efficient point of load solution. In steady state operation the LM2747 is always synchronous, even at no load, thus simplifying the compensation design. The LM2747 ensures a smooth and controlled start-up when the output is prebiased. The current limit protection does not require a current limit resistor in the power path, but is achieved by sensing the voltage VDS across the low side MOSFET. Though the control sections of the IC are rated for 3 to 6V (VCC), the driver sections are designed to accept input supply rails (VIN) as high as 14V. 2 Specifics of the Board This demo board targets the fixed and mobile telecommunications, industrial electronics, and distributed power markets. The demo board has a VIN range of 8V to 14V and a LDO regulator, the LP2937, powers VCC by regulating a 5V output voltage. The LM2747 regulates to an output range of 1.2V to 3.3V at 19A with a switching frequency of 300 kHz. Note, the demo board is optimized for the above parameters, thus for additional design modifications refer to the Design Consideration section of the LM2747 data sheet. The PCB is designed on four layers, the top and bottom layers are 2oz. copper and the two inner layers are 1oz. copper. The board measures 2.19 in. × 1.03 in. × 0.41 in. (56 mm × 26.2 mm × 10.3 mm) (l, w, h) on a FR4 laminate. 3 Feature Options When the tracking feature of the LM2747 is required for use, remove the jumper that connects the softstart capacitor C10 and connect the resistor divider, on designators R13 and R14, see Figure 1. The Track terminal has been provided for your connecting convenience. The demo board is synchronize ready, just connect an external clock to the SYNC terminal. Note, increasing the switching frequency results in a lower inductor current ripple and input and output voltage ripple (if the component values are kept the same). Monitor the MOSFET junction temperature since switching losses will increase, and do not exceed the maximum junction temperature of the MOSFET. Refer to the MOSFET manufacturer datasheet for maximum junction temperature specification and heat sinking guidelines. Connects SoftStart Capacitor SJ1 SJ1 Connects Tracking Resistors Figure 1. Soft-Start and Tracking Jumper All trademarks are the property of their respective owners. SNVA245A – May 2007 – Revised May 2013 Submit Documentation Feedback AN-1641 LM2747-19A Demo Board Copyright © 2007–2013, Texas Instruments Incorporated 1 Specification Summary 4 Specification Summary • • • • • • • • • • • • • • 5 www.ti.com Space saving footprint Wide ambient temperature range: -40 ºC to 65 ºC Input voltage range: 8V to 14V Adjustable output voltage: 1.2V to 3.3V No minimum load requirement Remote ON/OFF Power good signal Fixed switching frequency: 300 kHz Switching frequency synchronize range 250 kHz to 1 MHz Current Limit Protection Master power supply start-up tracking function Start-up with a pre-biased output load Adjustable soft-start Small size 2.19 in. × 1.03 in. × 0.41 in. (56 mm × 26.2 mm × 10.3 mm) Performance Characteristics Efficiency Figure 2. Efficiency vs. Load Current VOUT = 3.3V, fSW = 300 kHz 2 AN-1641 LM2747-19A Demo Board SNVA245A – May 2007 – Revised May 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated Switch Node Voltage and Output Voltage Ripple www.ti.com 6 Switch Node Voltage and Output Voltage Ripple Figure 3. VIN = 8V, VOUT = 3.3V, ILOAD = 100 mA, fSW = 300 kHz 20 MHz Bandwidth Limit Figure 4. VIN = 8V, VOUT = 3.3V, ILOAD = 19A, fSW = 300 kHz 20 MHz Bandwidth Limit Figure 5. VIN = 14V, VOUT = 3.3V, ILOAD = 100 mA, fSW = 300 kHz 20 MHz Bandwidth Limit Figure 6. VIN = 14V, VOUT = 3.3V, ILOAD = 19A, fSW = 300 kHz 20 MHz Bandwidth Limit SNVA245A – May 2007 – Revised May 2013 Submit Documentation Feedback AN-1641 LM2747-19A Demo Board Copyright © 2007–2013, Texas Instruments Incorporated 3 Load Transient Response 7 www.ti.com Load Transient Response 5A/DIV 2A/DIV 50 mV/DIV 50 mV/DIV 100 µs/DIV 100 µs/DIV Figure 7. VIN = 14V, VOUT = 3.3V ILOAD = 2A to 10A CH1: VOUT, CH2: ILOAD Figure 8. VIN = 14V, VOUT = 3.3V ILOAD = 11A to 19A CH1: VOUT, CH2: ILOAD 5A/DIV 2A/DIV 100 mV/DIV 100 mV/DIV 4 100 µs/DIV 100 µs/DIV Figure 9. VIN = 8V, VOUT = 3.3V ILOAD = 2A to 10A CH1: VOUT, CH2: ILOAD Figure 10. VIN = 8V, VOUT = 3.3V ILOAD = 11A to 19A CH1: VOUT, CH2: ILOAD AN-1641 LM2747-19A Demo Board SNVA245A – May 2007 – Revised May 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated Bill of Materials www.ti.com 8 Bill of Materials Table 1. Bill of Materials for LM2747 POL EVB (Vin: 8V to 14V, Vout: 3.3V, 19A) Location Part Number Type Size Parameters Qty Vendor U1 LM2747 Syn. Buck Controller TSSOP-14 Vin: 4.5V - 5.5V 1 Texas Instruments U2 LM27937IMP-5.0 Linear Regulator 5V, 500mA SOT-223 5V, 500mA 1 Texas Instruments L1 SER2010-202ML Inductor 2uH, 27A, 0.852mohm 1 Coilcraft Q1-2 IRF6633 N-MOSFET DirectFET-MP 20V, 16A, 4.1mohm, 11nC 2 Vishay Q3 IRF6609 N-MOSFET DirectFET-MT 20V, 150A, 2mohm, 46nC 1 Vishay D1 SL22-E3/2C Schottky Diode SMB 20V, 2A 1 Vishay D2 MBRS0520 Schottky Diode SOD123 20V, 0.5A 1 Vishay C1, 2 GRM32ER61C226KE20L Ceramic Capacitor 1210 22µF, 25V, X7R, 5% 2 Murata C3, 11 GRM319R71H104KA01B Ceramic Capacitor 1206 100nF, 25V, X7R, 10% 2 Murata C14 GRM319R71H474KA01B Ceramic Capacitor 1206 470nF, 25V, X7R, 10% 1 Murata C9 GRM1885C1H1210JA01 Ceramic Capacitor 0603 120pF, 50V, C0G, 5% 1 Murata C6 GRM188R71H222KA01 Ceramic Capacitor 0603 2.2nF, 50V, X7R, 10% 1 Murata C7 GRM1885C1H101JA01 Ceramic Capacitor 0603 100pF, 50V, C0G, 5% 1 Murata C8 GRM188R71H332KA01 Ceramic Capacitor 0603 3.3nF, 50V, X7R, 10% 1 Murata C10 GRM188R71H153KA01 Ceramic Capacitor 0603 15nF, 50V, X7R, 10% 1 Murata C12 GRM40X7R472K25 Ceramic Capacitor 0805 470nF, 25V, X7R, 10% 1 Murata C13 12066D226MAT Ceramic Capacitor 1206 22µF, 6.3V, X5R, 20% 1 AVX C4, 5 6SVPC220M OS-CON C6 220µF, 6.3V, 20% 2 Sanyo R1,18 CRCW06030R00F Chip Resistor 0603 0ohm 2 Vishay R2 CRCW06032151F Chip Resistor 0603 2.15k, 1% 1 Vishay R3, R17 CRCW06031002F Chip Resistor 0603 10k, 1% 2 Vishay R4 CRCW06032211F Chip Resistor 0603 2.21k, 1% 1 Vishay R10, 11 CRCW06031003F Chip Resistor 0603 100k, 1% 2 Vishay R5, 6, 8 CRCW06032R21F Chip Resistor 0603 2.21ohm, 1% 3 Vishay R7, 9 CRCW06034702F Chip Resistor 0603 47k, 1% 2 Vishay R12 CRCW06038451F Chip Resistor 0603 8.45k, 1% 1 Vishay R15 CRCW06031821F Chip Resistor 0603 1.82k, 1% 1 Vishay R16 CRCW060310R0F Chip Resistor 0603 10ohm, 1% 1 Vishay - - F-Pin - - Pin 90 deg., SIP, 6 way 8 Pitch: 2.54mm SNVA245A – May 2007 – Revised May 2013 Submit Documentation Feedback 1 AN-1641 LM2747-19A Demo Board Copyright © 2007–2013, Texas Instruments Incorporated 5 Demo Board Schematic 9 www.ti.com Demo Board Schematic SJ2 U2 LM2937 R18 VOUT VIN GND C13 C12 R16 C11 D2 VIN C14 R6 R17 R11 C2 U1 C1 R5 VCC SD SD PWGD LM2747 PWGD C7 SYNC Q2 Q1 HG BOO T R7 FREQ/SYNC LG R8 Q3 R10 SS/TRACK PGND SGND PGND D1 + C5 + C4 + C3 R9 EAO R13 VOUT L1 R15 I SEN FB TRACK R14 C9 SJ1 C8 C6 R2 R3 R12 C10 TRIM R4 SENSE Figure 11. 300 kHz Demo Board Schematic 6 AN-1641 LM2747-19A Demo Board SNVA245A – May 2007 – Revised May 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated PCB Layout www.ti.com 10 PCB Layout Figure 12. Top Silkscreen Figure 13. Top Copper Layer Figure 14. Bottom Silkscreen SNVA245A – May 2007 – Revised May 2013 Submit Documentation Feedback AN-1641 LM2747-19A Demo Board Copyright © 2007–2013, Texas Instruments Incorporated 7 PCB Layout www.ti.com Figure 15. Bottom Copper Layer Figure 16. Internal Layer-1 (GND Copper) Figure 17. Internal Layer-2 (GND Copper) 8 AN-1641 LM2747-19A Demo Board SNVA245A – May 2007 – Revised May 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. 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